The present invention relates generally to rack storage systems, and more particularly, to a cart return system that selectively and automatically cycles carts carrying unit loads, such as palletized loads, to the front of the system for unloading and then cycles the cart and unloaded pallet to their original position at the rear of the system in a single operation.
An important consideration in the storage or warehouse industry is the ability to safely and efficiently load and unload stored products while maintaining the highest possible storage density within a particular storage area. Another important consideration is whether the system can operate under the first in, first out inventory basis.
One such system is described in my U.S. Pat. No. 5,170,896 which is entitled "pallet return pallet rack system." In that system, two sets of rails, one located above the other, are used to cycle carts carrying pallets back and forth in the system. A cart with a loaded pallet is located at the front end of the system on the upper feed rails until the pallet is unloaded. A transfer mechanism is employed which enables the now unloaded pallet and cart to be transferred to a lower set of return rails which transport the cart to the rear of the system. Once the unloaded pallet and cart are transferred to the return rails, a loaded pallet and cart advance to take their place at the front of the system.
To continue the cycle, the unloaded pallet must first be removed by warehouse personnel from the cart on the return rails. The cart must then be placed on the upper feed rails, where a new loaded pallet can be added. Alternately, the unloaded pallet and cart can be removed and placed on the feed rails. The unloaded pallet must then be removed before a new loaded pallet can be added to the cart.
While unloading the pallet from the cart can be done in an efficient single step in this system, reloading cannot. As was discussed, reloading requires the removal of the unloaded pallet and the lifting of the cart to the feed rails before a new loaded pallet can enter the cycle, thus, limiting the efficiency of the system.